detective:
could you please provide the clarifications I asked for earlier in this threadSure, sorry I skipped you. I will answer now,
Adam and Eve were expelled from the Garden of Eden for being unrepentent sinners. Would they have put blame on someone else if they were repentant? So too, unrepentant sinners are expelled from the Christian congregation. Attending a meeting does not make the person part of the congregation.
Regarding Cain. Jehovah did the disfellowshipping. Later he named some men as judges, eventually, the elder arrangment was instituted in the 1st century.